totallimmortal

I plan on doing a s5 uim on my s4 as well as a few otehr things what i'm wondering is, is it possible to get the s4 motor to pull till 8k or would it have to be ported? right now i pull till like 7300 at least so i was hoping that a underdrive pully, header and s5 uim would help me pull closer to 8. also just out of curiosity, whats the highest rmp anyone has seen in person on a rotary and how high on a turbo one?

therotaryrocket

I think in australia they pull atleast 14,000 on 12a's but are N/A, also mazda tested a rotary(can't remember...3rotor?) at 28,000 rpms for 72 hours straight in a durability test that engine never broke they just ran out of 55 gallon jugs of fuel. My friend's S4 pulls a little past 7500 before it hits the rev-limiter, I know the s5 rotors are lighter and higher compression so i'm sure it has better highend. RX-8's Renisis does atleast 9,500 rpms.

i.didnt.do.it

dont forget that the stock tach isnt accurate at that high of rpm range, when you say your pulling till 7300, your prolly around 7600+/-

therotaryrocket

does someone know why the gauges aren't accurate at that rpm? I always hear that, and the speedometer too, but i cant under stand an inaccurate cable driven speedometer, just the gauge itself i guess.

totallimmortal

well my safc tells me my rpm too, and about this rev limiter some people say there is one some say there isn't, i'v had my motor probably around 9k by accident quite a few times, (3rd gear misses some times) and i've been unable to find any limiter, but back to the main question how high can a stock port s4 make power?

13bSav

I have tapped 8000rpm in my s4 with gutted cats, exhuast and intake. Ive also hit 8000 stock..=D

vice

dont out cars have a rev limiter at 8 grand? cuz thats as high as i can go.

Bob_The_Normal

From rumor I think the S4 limiter is at 8.3k (I'm going off bad memory here) and the S5 is at 9k.

I've never HIT the limiter, but I've gone through that loud buzzer thing fearlessly to 9... and repeatedly... I doubt the engine would have any problems after that... but I'm a tall guy, I'd like to stay that way.

--Gary

Dan H

Uhh...no....



Anyways, to take advantage of it, you need to port the engine to make some decent power up top. Theres no point of overrevving on a stock engine when there is no power to be made past the powerband.

I'd be weary of revving over 9K rpm's too. Remember, that the higher revving S5 engines had hardened stationary gears too.

totallimmortal

so how high can i make power on the stock ports? I know that if i port i'll have a higher powerband but i'm not gonna port it yet. I'm not trying to rev high to be cool its just that from 5k-7k my car pulls really really hard and if i could get it to pull to 8k i know i'd love it. i'm not trying to go any higher than 8k anyway so i'm not woried about stationary gears right now. Also 28000 rpm? thats hard to believe especially fot 72 hours but if anyone has any more info on any high reving rotaries i'd love to read about em or even see a video clip of someone hitting like 12 grand on the tach, that has to sound crazy at 12k

therotaryrocket

here's one....but it's an IF

casio

yes, but look at F1 engines now. they're V8s spinning 15,000+- rpm. thats twice what a dohc cobra engine spins (only high-revving v8 i know of). they don't last too long that i know of. as for us rotaries, we can spin fast, have no valvetrain, but 25,000rpm is fast. i believe at 10,000 a scattershield is required for most racing organizations.
either way, "what if" and saying mazda tested .. at 28,000 rpm are two different things. if there's proof, then there's proof, but that's different than a "what if" scenario. i can't imagine what ignition and computer would be used to control 28,000 rpm.

therotaryrocket

this is quoted from a 4 stroke chain saw forum
"I seem to recall Sachs-Dolmar once made a chainsaw with a rotary engine in it, it was designated the KMS-4 model. 59cc and about the same HP as a 3120 or an 088. I would like to have one but theyre so hard to come by. The wankel engine was utilized by the kms4 model and I think it was a fairly strange design to say the least. Lets suggest they build chainsaws with wankel engines again! they're more powerful, lighter, probably quieter, can be modified to rev to around 28K rpms, a friend in high school taught me this, the only downside is that they use more fuel at a higher rate of consumption."

OK so the chain saw is a little farfetched, but I swear I read that this japenese guy high in the ranking of mazda tested an engine like that. It was in the 1st gen section I think where this guy purposely blew his engine, which was already half blown or something, by revving as high as possible for as long as possible which I believe was like 9K. Later in that post someone mention that 28k rpm or maybe 22k rpm im not sure. I'm still looking for proof.

Dan H

Well, if you open up the exhaust like you said and with a decent intake, I'd bet you can take it 7.5K and maybe (just maybe) 8K but you should put it on the dyno to see if its really making power up there. If not, then theres no point.

Dan H

But thats a chainsaw engine. Small engines can rev high but a torque curve is important too. Even most peripheral ported engines see around 10-11K rpm's. Some past engines like the IMSA GTU car (FB) have been known to go 13K.

therotaryrocket

aww forget it, i'm tired of searching!!!sorry for claiming and not backing it up. But i'm sure 13k rpms is good enough for almost anyone.

casio

yea, the DKM motors spun at probably twice that, but they were more like superchargers than engines. there's a rotary for RC cars, too, that spins at crazy speeds, but its about the size of a penny. in fact, some of those small rotaries dont even have seals i believe. the RC one i think is just a rotor and shaft.
13K is more than enough for most people. i cant imagine a torque curve for 28,000rpm since, if i'm not mistaken, tq and hp cross paths every 5252rpm.

fc3s-gxl

hey totalimmortal ur car is a non turbo right? if so y do u have a 3 inch exhaust, for all motor u want smaller, u need alot of back pressure when running all motor . (ive noticed alot of ppl run 3 inch exhaussts on their all motors here,why?3inches is for turbo cars ,

sudseh

err as far as i remember, for the rotary you either want no backpressure so that all the old combustion stuff gets evacuated or else a tuned system to preserve the emissions.
suds

Dan H

There is no rotary for RC cars and none that is the size of a penny for RC use. But there is a rotary for RC airplanes. According to OS engines, it makes 1.27hp at 17,000rpm's in .30 displacement. It even has apex seals too. One of my .12 2 stroke piston engine for my RC makes about the same horses but spins over 30,000rpm's.

casio

yea, here's the airplane one:
http://www.osengines.com/engines/osmg1400.html
Displacement: 0.303 cu in (5.0 cc)
Practical rpm: 2,500-18,000
Output: 1.27 hp @ 17,000 rpm
Weight: 11.8 oz (335 g)

and i was referring to this, sorry.
http://www.berkeley.edu/news/media/r.../02_engin.html



not for RC use.

Dom_C

Learn a bit bout rotorys. . . 3 inch may be overkill, but for an N/A Intake and exhaust are everything. In those piston pushers if you don't have the proper amount of backpressure you're valves and junk may not seat correctly, but we don't ahve to deal with that ****. The free'r the flowing the better.

casio

and how to spell "rotaries."

totallimmortal

yeah i experimented with different exhaust and jumped from 16.3 to a 15.2 in the 1/4 with that exhuast so i kept it, there was a slight loss of low end but who gives a **** when you launch at 7k

rs_1101

simple. entropy.

think about it. you have a signal at 1krpm. you can hear that. now 4krpm, is 4 times faster than the 1krpm. then 7500 krpm are almost twice as fast as 4k.. just think about it for a second. a mechanical guage, that is driven by a rudimentary voltage signal sent from a 17 year old computer thats reading a 17 year old trailing coils signal.

do you see room for error here? especially at 7500 rpm? (which is a godawfully high rpm for most cars)